JPH04298683A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a misfire detecting device of an internal combustion engine capable of judging misfire during ignition term and having excellent mounting facility and maintenance property. CONSTITUTION:A misfire detecting device 4 is provided with an electric conductor 41 arranged close to the secondary circuit of an ignition circuit between a distributor 2 and spark plugs 3, a measuring circuit 42 for induced electromotive force generated in the electric conductor 41 by discharge current in the secondary circuit, and a microcomputer 43 previously memorizing data of correlation between the voltage waveform of the induced electromotive force and the ignition condition of an engine combustion chamber, and the voltage waveform of induced electromotive force generated in the electric conductor is compared with the pattern of induced electromotive force of the data to detect normal ignition, ignition miss, or spark discharge miss.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is a misfire detection device for detecting ignition errors (misfires) in an internal combustion engine equipped with an ignition device that supplies high voltage generated by an ignition coil to a spark plug via a power distributor. Regarding.

0002

2. Description of the Related Art In response to demands for purifying the exhaust gas of automobile engines and improving fuel efficiency, there is a need for a device that can detect the ignition state of each cylinder of the engine and take measures to prevent misfires in all cylinders. As a misfire detection device, conventionally known methods include drilling a hole in the cylinder block and attaching a combustion light sensor, attaching a pressure sensor to the seat of a spark plug, and measuring the ion current of the ignition circuit.

0003

[Problems to be Solved by the Invention] However, with the conventional method, it is difficult to determine whether a misfire has occurred during the ignition period of the ignition stroke that begins with the spark discharge of the spark plug, and it is troublesome to install. However, there were drawbacks such as installation being troublesome and maintenance required to install it on all cylinders of all vehicles. An object of the present invention is to provide a misfire detection device for an internal combustion engine that is capable of determining misfire during the ignition period and is easy to install and maintain.

0004

[Means for Solving the Problems] The misfire detection device of the present invention uses a conductive wire disposed close to a high-voltage electric wire between a spark plug and a power distributor installed in a secondary circuit of an ignition circuit. a circuit for measuring the induced voltage generated in the conductor due to the discharge voltage generated in the secondary circuit; and a microcomputer in which data on the correlation between the induced voltage waveform and the ignition state of the engine combustion chamber is stored in advance. and detects normal ignition, ignition error, and spark discharge error by comparing the induced voltage waveform measured by the measurement circuit with the data.

[0005]

[Operation] In this invention, a conductor is insulated and arranged along the high voltage wiring on the spark plug side from the rotor gap of the power distributor in the secondary circuit of the ignition circuit, and the pattern (voltage waveform) of the generated high voltage is Measured by induced voltage generated in a conductor. This induced voltage pattern (induced voltage waveform) is compared with data patterns such as normal ignition, misfire, and spark discharge errors that have been measured or calculated in advance. This detects normal ignition, ignition error, and spark discharge error, and outputs the information to control means for controlling ignition advance, fuel injection timing, air-fuel ratio, etc., and takes measures to prevent misfires for each cylinder.

[0006]

Effects of the Invention This misfire detection device is capable of determining a misfire during the ignition timing, and can be used to prevent misfires such as another spark discharge immediately after a single ignition timing. Additionally, by simply installing a short conductor along the secondary circuit of the ignition circuit, the rest can be handled by electronic circuitry. Therefore, a misfire detection device that is easy to install and that is maintenance-free can be obtained. Further, in claim 2, a diode is interposed between the conductor and the measuring circuit to cut off the secondary voltage of the ignition coil, so that the secondary voltage of the ignition coil leaks to the conductor and destroys the measuring circuit. This can be prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an ignition system 100 for an internal combustion engine, which includes an ignition coil 1 having a primary coil 11 and a secondary coil 12 to which a battery B and an interrupter E are connected, a power distributor 2, and a spark plug 3. , the secondary coil 12 is equipped with the misfire detection device 4 of the present invention.

The misfire detection device 4 includes a conductor 41 as a sensor mounted close to the high voltage cord 21 connecting the power distributor 2 and the spark plug 3, a signal processing circuit 42,
It consists of a microcomputer 43, and a high voltage diode D is provided between the conductor 41 and the signal processing circuit 42. The microcomputer 43 outputs an output to a monitor circuit M to make the driver aware of the occurrence of a misfire, and also outputs to a control means N such as an engine ignition timing adjustment device, a fuel injection timing control device, an air-fuel ratio control device, etc. Prevent misfires from occurring.

The conductor 41 is a means for detecting the secondary voltage generated in the secondary circuit of the ignition circuit, and is used in plug caps, high voltage cords (plug cables), distributor caps, spark plugs, high voltage cord clampers, etc. attached to produce an induced voltage corresponding to the secondary voltage waveform. The high voltage diode D cuts off the secondary voltage of the ignition coil between the conductor 41 and the signal processing circuit 42, and
This prevents the voltage from leaking into the conductor 41 and destroying the measurement circuit.

The signal processing circuit 42 includes a clamp circuit 44 connected to the conductor, a waveform shaping circuit 45 that inputs the output of the clamp circuit 44, a counter 46 that counts the pulses output from the waveform shaping circuit 45, and the waveform shaping circuit 44. It consists of a peak hold circuit 47 that holds the level of the final pulse of the circuit 45 for a predetermined time, and an AD converter 48.

Next, the operation of this misfire detection device will be explained with reference to FIG. When a spark does not fly, the discharge voltage of the spark plug 3 has one large peak, followed by small voltage fluctuations. When spark discharge and ignition occur normally, one low peak voltage is generated, followed by a low voltage waveform containing a small number of peaks. Furthermore, when a spark discharge occurs but does not ignite due to a lean mixture of fuel and air, a large peak is followed by a plurality of medium and small peaks.

As a result, in the conductor 41, when a spark discharge error occurs, one high induced voltage waveform as shown in A1 occurs, and when ignition and combustion occur smoothly, a small number of low peak voltage waveforms as shown in A2 occur. Occur. A3 and A4
This is the waveform when there is an ignition error, in which the spark flew normally but the ignition did not occur, and multiple peak voltages of large, medium, and small occur.

The clamp circuit 44 converts the peak voltage into B
1, B2, B3, and B4. The waveform shaping circuit 45 adjusts the voltage waveforms B1 to B4.
Among them, the waveforms above the set level are C1, C2, C3.
, C4. A counter 46 counts the number of pulses within a certain period of time T1 from the ignition timing, converts the pulses into a voltage according to the wave number, and outputs the voltage. Further, the peak hold circuit 47 holds the level of the final pulse within a certain time T1 for a time T2, and
, D3, and D4. The A-D converter 48 converts these outputs into digital signals, which are analyzed by the microcomputer 43 to determine whether there is ignition or not, and whether there is a mistake in sparking.

Discrimination between spark discharge error, normal ignition, and ignition error is made based on the following criteria. If there is only one pulse and the peak held voltage value is high, there is a spark discharge error. Normal ignition occurs when there are few pulses and the peak held voltage value is low. If the pulse is 2 or more and the peak held voltage value is medium, there is an ignition error. By analyzing the phenomenon occurring in the discharge waveform of the secondary voltage from two viewpoints and determining misfire in this way, misfire detection can be performed accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a misfire detection device according to the present invention.

FIG. 2 is a waveform diagram for explaining operation.

[Explanation of symbols]

1 Ignition coil 2 Power distributor 3 Spark plug 4 Misfire detection device 41 Conductor 42 Signal processing circuit 43 Microcomputer

Claims (2)

[Claims] Claim 1: A misfire detection device for an internal combustion engine comprising an ignition device that supplies high voltage generated by an ignition coil to a spark plug via a power distribution device, which includes a power distribution device installed in a secondary circuit of an ignition circuit and a spark plug. A conductor disposed close to the high voltage wiring between the plug and the plug, a circuit for measuring the induced voltage generated in the conductor due to the discharge voltage generated in the secondary circuit, and a circuit that measures the induced voltage waveform and the engine combustion chamber. The internal combustion engine is equipped with a microcomputer in which data relating to the ignition state is stored in advance, and the induced voltage waveform measured by the measurement circuit is compared with the data to detect normal ignition, ignition error, and spark discharge error. Engine misfire detection device. 2. A misfire detection device for an internal combustion engine according to claim 1, wherein a diode for cutting off the secondary voltage of the ignition coil is interposed between the conductor and the measuring circuit.